1. [SII] Observations and what they can tell us Snippets of possibly useful stuff by Lesa Moore 31 st October 2012

2. 2 Forbidden lines Lifetime in excited states Lifetime in excited states Lyman  : 10 -8 s Lyman  : 10 -8 s [SII]: 3846 s and 1136 s [SII]: 3846 s and 1136 s Forbidden lines appear in low-density gas: Forbidden lines appear in low-density gas: for transitions that have long lifetimes in excited states [SII], [NII], [OII], [OIII] for transitions that have long lifetimes in excited states [SII], [NII], [OII], [OIII] where there are too few collisions to de-excite collisionally (< a few hundred thousand cc -3 ) where there are too few collisions to de-excite collisionally (< a few hundred thousand cc -3 )

3. 3 Spectra on the CCD OI sky emission at 5577Å OH sky emission bands

4. 4 Wavelength-Calibrated Galaxy Spectrum

5. 5 Most common emission lines “A brief introduction to narrowbanding” “A brief introduction to narrowbanding” http://www.astros urf.com/brego- sky/A_glimpse_to_ the_night_sky/Arti cles_files/what_is. pdf http://www.astros urf.com/brego- sky/A_glimpse_to_ the_night_sky/Arti cles_files/what_is. pdf http://www.astros urf.com/brego- sky/A_glimpse_to_ the_night_sky/Arti cles_files/what_is. pdf http://www.astros urf.com/brego- sky/A_glimpse_to_ the_night_sky/Arti cles_files/what_is. pdf

6. 6 Targets Emission nebulae Emission nebulae Planetary nebulae Planetary nebulae Supernova remnants Supernova remnants

7. 7 Exercise 3 http://web.williams.edu/astronomy/research/ PN/nebulae/exercise3.php http://web.williams.edu/astronomy/research/ PN/nebulae/exercise3.php http://web.williams.edu/astronomy/research/ PN/nebulae/exercise3.php http://web.williams.edu/astronomy/research/ PN/nebulae/exercise3.php Ratio of intensities of [SII] lines Ratio of intensities of [SII] lines 6716 to 6731 6716 to 6731 can indicate gas density can indicate gas density Low density: Ratio is statistical weight (how many electrons the level can hold) High density: Shorter lifetime (6731) makes stronger line In between, ratio describes actual gas density

8. 8 SNR in the Magellanic Clouds http://www.mcsnr.org/about.aspx http://www.mcsnr.org/about.aspx http://www.mcsnr.org/about.aspx SNR classification - meet at least two of the following criteria: SNR classification - meet at least two of the following criteria: Diffuse nonthermal radio emission Diffuse nonthermal radio emission Diffuse thermal X-ray emission Diffuse thermal X-ray emission High [SII]/H  ratio (> 0.4) and/or high optical expansion velocity High [SII]/H  ratio (> 0.4) and/or high optical expansion velocity

9. 9 SNR in M31 http://aas.org/archives/BAAS/v25n2/aas182/abs html/S219.html http://aas.org/archives/BAAS/v25n2/aas182/abs html/S219.html http://aas.org/archives/BAAS/v25n2/aas182/abs html/S219.html http://aas.org/archives/BAAS/v25n2/aas182/abs html/S219.html High [SII]/H  implies likely SNR High [SII]/H  implies likely SNR Ratio is not very high for many SNRs Ratio is not very high for many SNRs Complementary test based on a comparison of the H  flux and the presence or absence of hot, ionizing stars Complementary test based on a comparison of the H  flux and the presence or absence of hot, ionizing stars Combined BVRI, H , [SII] data has revealed ~200 objects which are candidate SNRs throughout M31 based on this test Combined BVRI, H , [SII] data has revealed ~200 objects which are candidate SNRs throughout M31 based on this test

10. 10 Optical Imaging and Spectroscopic Observation of the Galactic Supernova Remnant G85.9-0.6 http://arxiv.org/pdf/0909.2959v1.pdf http://arxiv.org/pdf/0909.2959v1.pdf http://arxiv.org/pdf/0909.2959v1.pdf Images taken with narrow-band interference filters H and [SII] and their continuum. Images taken with narrow-band interference filters H and [SII] and their continuum. [SII]/H  ratio image is performed [SII]/H  ratio image is performed Ratio ~0.42, indicating that the remnant interacts with HII regions. Ratio ~0.42, indicating that the remnant interacts with HII regions. [SII] 6716/6731 average flux ratio from spectra [SII] 6716/6731 average flux ratio from spectra electron density N e is obtained to be 395 cm −3. electron density N e is obtained to be 395 cm −3. [OIII]/H  ratio [OIII]/H  ratio shock velocity has been estimated shock velocity has been estimated pre-shock density of n c = 14 cm −3 pre-shock density of n c = 14 cm −3 explosion energy of E = 9.2 × 10 50 ergs explosion energy of E = 9.2 × 10 50 ergs interstellar extinction of E(B−V ) = 0.28 interstellar extinction of E(B−V ) = 0.28 neutral hydrogen column density of N(HI) = 1.53 × 10 21 cm −2 neutral hydrogen column density of N(HI) = 1.53 × 10 21 cm −2

11. 11 Observations

12. 12 SNR IMAGES

13. 13 The final image The negative if the [SII]/Ha image of G85.9-0.6 (smoothed) The negative if the [SII]/Ha image of G85.9-0.6 (smoothed)

14. 14 SNR SPECTRA

15. 15 Measurements

16. 16 Conclusions from image